Ring stator motor device

ABSTRACT

An integrated drive motor assembly is described where the functional components of a powered device are an integral part of the motor. The assembly comprises a brushless, direct current drive motor having a ring-shaped stator with flat printed circuit coil windings, a ring-shaped permanent magnet rotor, and an electronic commutator circuit. Functional embodiments of the assembly include a rotor impeller and an axial flow fan.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of priority of U.S.Provisional Patent Application serial No. 60/311,297, filed Aug. 10,2001 for Edward Lopatinsky, et al. the entire content of which isincorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a brushless DC motor device andmore particularly to a permanent magnet brushless motor assembly.

BACKGROUND OF THE INVENTION

[0003] Brushless DC motors in various forms are well known in the art asdescribed, for example, in U.S. Pat. Nos. 4,228,384 and 6,307,337. Suchmotors use an electronic controller instead of an armature commutatorand brush assembly to switch the flow of current to individual motorwinding coils.

[0004] A major limiting factor in the performance of conventional DCmotors is internal heating, where the heat generated in the iron-coredcoils of the motor armature escapes via an inefficient thermal paththrough the shaft and bearings of the motor assembly or through theairgap between the armature and field magnets to an outer casing.

[0005] In a brushless DC motor, the motor armature is a permanent magnetrotor assembly and the stator comprises a group of wound iron corecoils. For better cooling, the stator coils are positioned in a casingto provide a short, efficient, thermal path to the outside air. Coolingcan further be improved by blowing air over the casing and addingheat-removing fins. This ease of cooling allows a brushless motor toproduce a much higher power in relation to its size than a motor with aconventional brush and commutator assembly.

[0006] A major advantage of brushless motors is their lack ofconventional commutator and brush hardware. These items are a source ofwear and may require frequent maintenance.

[0007] Brushless motors have certain disadvantages. For example, inorder to drive a brushless motor, control electronics are necessary toselectively switch current through appropriate motor winding coils. Thecircuitry is often complex in order to provide the necessary timingsequence. In addition, the use of wound iron-core coils increases theweight and size of the motor assembly. Further, eddy current lossesproduced in iron-core coils reduce motor efficiency. These factorsincrease the manufacturing cost of devices using brushless motortechnology.

[0008] Typically, a drive motor is connected to another assembly toperform a useful function. A motor, for example, may be connected to afan, pump, or other type of device to provide operating power for thedevice.

[0009] Integrated assemblies can be made, however, using brushless drivemotor technology, where the functional components of a powered deviceare an integral part of the motor assembly.

[0010] Accordingly, a need exists for an improved integrated brushlessdirect current motor device that does not use iron core coils, is easilycooled, and is compact and economical to manufacture.

BRIEF SUMMARY OF THE INVENTION

[0011] An integrated direct current, brushless motor assembly isdescribed where the functional components of a powered device are anintegral part of the motor. The device comprises a novel ring-shapedstator assembly with flat, printed circuit type coil windings, apermanent magnet ring-shaped rotor assembly disposed within the statorassembly and an electronic stator coil commutator circuit.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0012]FIG. 1 is a structural view of a ring type motor of the invention;

[0013]FIG. 2 is an axial cross-sectional view of a rotor and statorassembly of the invention;

[0014]FIG. 3 is a schematic diagram of a single-phase stator coilcircuit of the invention;

[0015]FIG. 4 is a schematic diagram of a three-phase stator coil circuitof the invention;

[0016]FIG. 5 is a functional diagram of a switch pattern for athree-phase commutating circuit of the invention;

[0017]FIG. 6 is a continuation of the functional diagram of FIG. 5;

[0018]FIG. 7 is a structural view of an axial fan embodiment of theinvention; and

[0019]FIG. 8 is a structural view of a fluid impeller embodiment of theinvention;

[0020]FIG. 9 is an illustrative view of a band of stator coils of theinvention; and

[0021]FIG. 10 is a structural view of an integrated stator coilassembly.

DETAILED DESCRIPTION OF THE INVENTION

[0022] With reference to FIG. 1, one embodiment of the rotor and statorassembly of a motor of the invention comprises a ring-shaped stator 10with a plurality of flat printed circuit coil windings 11circumferentially positioned around the stator periphery, and arotatable rotor assembly 14 having a ring-shaped rotor band 15 with aplurality of permanent magnets 18 circumferentially positioned aroundthe rotor band periphery. The diameter of the stator ring is chosen tobe slightly larger than the diameter of the rotor band.

[0023] A magnetic bridge 12, comprising a continuous spiral wrapping ofsoft iron wire or laminated bands of soft iron, surrounds the stator toconnect and concentrate magnetic flux between the coil windings and therotor magnets. The magnetic bridge is fixed in close proximity to thestator but may also be manufactured as a movable part that ismechanically connected to the rotor assembly.

[0024] As shown in FIG. 1, the stator 10 and magnetic bridge 12 can besecured to a mounting surface by one or more suitable fasteners 13.

[0025] The printed circuit stator coils are flat, spirally wound coilsof copper or other electrically conducting material placed in closeproximity to each other along a ring-shaped substrate of electricallyinsulating material. The coils can be coated with a nickel-gold plating,for example, to increase the magnetic attraction between the coils andthe rotor magnets and to align the coils and magnets to an appropriatemotor-starting position. If necessary, a band of stator coils can bemechanically and electrically joined to another band of coils to form alarger diameter stator. In addition, the bands can be layered with thecoils of one circuit directly aligned and electrically phased with thecoils on another circuit, to generate stronger like magnetic poles andincrease the magnetic field strength.

[0026] The layered coils can also be electrically connected in series toincrease the overall stator resistance, allowing the stator to operateat higher voltages.

[0027] An electronic commutator circuit is connected to the motor statorcoils to selectively switch the flow of electrical current to individualgroups of coil windings. The circuit can be a type H-bridge drivecircuit, for example, and can be included as a printed circuit assemblyattached to the stator.

[0028] The rotor assembly 14 is centrally positioned within the statorand comprises a ferrous, ring-shaped, rotor band 15 with a plurality ofperipherally placed permanent magnets 18. The rotor band serves touniformly direct the flux paths of the permanent magnets to improvemotor performance.

[0029] The direction of magnetization of the rotor magnets is radial andthe magnets are arranged around the rotor band in a configuration ofalternating magnetic poles.

[0030] A strut structure 16 is attached to the rotor band and supports acentral axis hub 17. The hub may include a suitable axle and bearingassembly to support the rotor assembly and provide coupling to a powereddevice.

[0031] The motor operates when electromagnetic torque energy, developedby interacting magnetic fields between the rotor and stator, causesrotation of the rotor hub, as is well known in the art.

[0032] With reference to FIG. 2, a longitudinal section of the rotor andstator assembly of a motor of the invention is illustrated. In thisembodiment, the stator magnetic bridge is fixed in close proximity tothe stator.

[0033] A ferrous ring-shaped rotor band 22 has a plurality ofradially-magnetized permanent magnets attached around its outerperiphery with each adjacent magnet having the opposite polarity. Forexample, as shown in FIG. 2, a north-south polarity magnet 23 is placedadjacent to a south-north polarity magnet 24.

[0034] The stator ring 25 is located in close proximity to, but nottouching, the rotor magnets and is made of an electricallynon-conductive substrate material with a layer of flat printed circuitcoils 26 bonded to the underside of the substrate and another layer offlat printed circuit coils 27 bonded to the top side of the substrate.Individual coils on each layer can be electrically connected together,through the substrate, using via's or copper plated holes, as is wellknown in the art.

[0035] In one embodiment of the stator, individual coils are placedadjacent to each other with each coil being wound in the oppositedirection. In this configuration, when current is commutated through thecoils, like magnetic poles are created on two adjacent coils at any onepoint in time, forming one stator magnetic pole.

[0036] Located on the outer periphery of the stator ring is a magneticbridge formed by a continuous wire wrapping of a first layer 20 offerrous wire and a second layer of ferrous wire 21. The magnetic bridgeis separated from the stator coils by a thin ring of nonconductivematerial 28.

[0037] With reference to FIG. 3, a single-phase stator coil circuit isillustrated. The coils are connected in series to form a continuouscircuit with adjacent coils having opposite polarities. In thisconfiguration, each of the rotor's permanent magnets is oriented in thesame polarity. A stator magnetic bridge is not necessary to bridge therotor and stator's magnetic flux paths.

[0038] As shown in FIG. 3, two electrical connections are required tooperate the stator circuit and a full bridge type electronic commutatorcircuit can be used to switch all coils at the same time.

[0039] With reference to FIG. 4, a three phase stator coil circuit isillustrated. A three-phase Y configuration is shown but the stator coilsmay be connected in either a Delta or a Y circuit configuration.

[0040] The numbers on each coil represents the physical location of thecoil in reference to other coils placed around the stator. The arrowsrepresent the turn direction of each coil winding.

[0041] The phase connection points A, B and C indicate the electricalconnection points to a specific group of stator coils. Phase A coils1,4,7,10,13,16,19,22,25,28,31, and 34, for example, are shown combinedwith the coils of phases B and C.

[0042] In operation, when current is passed through phases A and B,adjacent coils 1 and 36, 4 and 3, etc. each in turn create one commonmagnetic pole. Similarly, common magnetic poles are created with phasesA and C when current is passed through adjacent coils 1 and 2, 4 and 5,etc.

[0043] By switching the three phases of the stator in the propersequence, a continuously rotating magnetic field around the stator ringcan be created. In addition, the direction of motion of the rotor can bechanged by altering any one of the stator's electrical phaseconnections.

[0044] With reference to FIGS. 5 and 6, commutator switching logic for athree-phase stator coil circuit of the invention is shown. Switches S1through S6 generate the proper switching sequence and are illustrated ascommon mechanical switches. In actual practice the switches are replacedby solid state switching devices including power transistors, MOSFET's,or IGBT's.

[0045] The stator coil switching sequence to complete one three-phasecycle is shown. Six steps are required to complete the cycle where eachstep represents the transition of a rotor magnet to a different pair ofcoils around the stator.

[0046]FIG. 5 illustrates the first step in the cycle with switches S1and S5 closed to allow current to flow through Phase A and Phase B coilwindings. At this time, Phase C coils have no current flowing throughthem. The second step in the cycle has switches S I and S6 closedallowing current to flow through Phase A and Phase C coils. Phase Bcoils have no current passing through them at this time. The third stepin the cycle has switches S2 and S6 closed allowing current to flowthrough Phase B and phase C coils. Phase A coils at this time have nocurrent flowing through them.

[0047]FIG. 6 illustrates the fourth step in the cycle with switches S2and S4 closed allowing current to flow through Phase B and Phase Acoils. Phase C coils have no current passing through them. At this time,current is flowing through the same coils as in the first step of thecycle, but in the reverse direction. Accordingly, Phase A and Phase Bcoils have reversed magnetic polarities from the polarities in the firststep of the cycle. The fifth step in the cycle has switches S3 and S4closed allowing current to flow through Phase C and Phase A coils. PhaseB coils at this time have no current passing through them. At this time,current is flowing through the same coils as in the second step of thecycle, but in the reverse direction. Accordingly, Phase C and Phase Acoils have reversed magnetic polarities from the polarities in thesecond step of the cycle. The sixth step in the cycle has switches S3and S5 closed allowing current to flow through Phase C and Phase Bcoils. Phase A coils have no current passing through them. At this time,current is flowing through the same coils as in the third step of thecycle, but in the reverse direction. Accordingly, Phase B and Phase Ccoils have reversed magnetic polarities from the polarities in the thirdstep of the cycle.

[0048] The stator coil commutator completes one full switching cycleupon completion of the sixth step in the switching sequence to cause acomplete rotation of the rotor assembly. The cycles are repeated forcontinuous rotation of the rotor.

[0049] The commutator may be a solid-state device using, for example,bi-polar transistors or power MOSFET,s to switch current through thestator coils.

[0050] The rotor position, used for timing in the commutation process,may be sensed by one or more magnetic Hall Effect devices using existingmagnets on the rotor assembly or by using a separate array of magnetsarranged for this purpose. Other types of position sensors includingoptical sensors may also be used.

[0051] The rotor hub of the invention may include a suitable axle andbearing assembly to deliver electromagnetic torque energy to a deviceconnected to the axle. The rotor, however, may also be formed as part ofan impeller or fan assembly where the torque energy of the rotating hubis used directly and is not transferred by a shaft to an externaldevice.

[0052] With reference to FIG. 7, an integrated fan assembly of theinvention is shown. The rotor strut structure 31 of the motor assemblyis attached to the rotor band 32 and is configured as blades of an axialflow fan. In this embodiment, the diameter of the rotor central hub 30is minimized to reduce blockage of the air stream and increase theairflow area. A bell mouth structure 33 can be added to the assembly tocontrol the airflow path.

[0053] With reference to FIG. 8, an integrated fluid impeller embodimentof the invention is shown where the impeller blades 40 are made from aplastic magnetic material and the rotor hub 42 is made of a feffousmaterial. In this embodiment, the impeller blades 40 and the rotor hub42 form a rotor assembly. A stator magnetic bridge 41 is fixed to thestator 44 and does not rotate with the rotor assembly. A bell mouthstructure 43 may be included to direct the fluid flow and providesupport for the stator.

[0054] The stator coil assembly of the invention can be fabricated as asingle layer of coil windings, located on the top and bottom sides of asubstrate, with each layer comprising several pairs of coil windings.

[0055] As shown in FIG. 9, each pair of coils 50 is made as a spiralwinding extending from the center of a start coil winding 51 to a centerof an end coil winding 52 with the same turn direction of the spiral inrelation to each coils center. The layers of coil windings are the samein a transparent view and are shifted linearly so that the center of thestart coil windings on the top side of the substrate are electricallyconnected to the center of the end coil windings on the bottom side ofthe substrate using via's or copper plated holes through the substrate.The circuit of one layer of coil windings can be interrupted (broken) toprovide connecting power leads to a commutator circuit.

[0056] The stator coil assembly can also be integrated with a housing orfan shroud of a motor of the invention.

[0057] With reference to FIG. 10, a thin wall plastic ring substrate 60is formed as part of a housing or shroud assembly 61. The substrate canbe rolled with a thin laminate of copper or can be electricallydeposited with copper along the inside and outside circumferences of thering. The stator coils are etched or electrically deposited usingprinted circuit board fabrication techniques on the inner circumference62 and outer circumference 63 of the ring using a UV light photoexposure or silkscreen method.

[0058] Although the various features of novelty that characterize theinvention have been described in terms of certain preferred embodiments,other embodiments will become apparent to those of ordinary skill in theart, in an objective view of the disclosure herein. Accordingly, thepresent invention is not intended to be limited by the recitation of thepreferred embodiments, but is instead intended to be defined solely byreference to the appended claims.

What is claimed is:
 1. A direct current brushless motor device comprising: a ring-shaped stator assembly having a plurality of circumferentially placed printed circuit coil windings; a rotatable ring-shaped magnetic rotor assembly disposed within said stator assembly said magnetic rotor assembly having supporting structure for a central axis hub; a plurality of permanent magnets circumferentially placed around said rotor assembly said permanent magnets producing a radially-directed magnetic field; and an electronic commutator circuit connected to said printed circuit coil windings whereby electric current is selectively switched by said commutator circuit through said coil windings to generate a rotating magnetic field whereby electromagnetic torque-energy developed by interacting magnetic fields of the rotor and stator assemblies causes rotation of the rotor assembly around the rotor central axis.
 2. A motor stator coil assembly comprising a ring-shaped band of electrically insulating material having circumferentially placed printed circuit coil windings, said coil windings operative to generate a magnetic field in response to the flow of electrical current through said coil windings, said magnetic field operative to interact with a magnetic field of a rotor assembly of a motor, said interacting magnetic fields causing rotation of said rotor assembly.
 3. The motor stator coil assembly of claim 2 wherein said printed circuit coil windings comprise a band of flat, spirally wound copper coils electrically interconnected and placed in close proximity to each other.
 4. The motor stator coil assembly of claim 2 wherein said printed circuit coil windings are connected in series to increase the electrical resistance of the coil windings.
 5. The motor stator coil assembly of claim 2 wherein said printed circuit coil windings comprise two or more layered bands of aligned and electrically phased coils.
 6. The motor stator coil assembly of claim 2 further comprising a printed circuit electronic commutator circuit operatively connected to said printed circuit coil windings to selectively switch the flow of electrical current through said coil windings.
 7. The direct current brushless motor device of claim 1 wherein said electronic commutator circuit comprises a full bridge stator coil drive circuit.
 8. The direct current brushless motor device of claim 1 wherein said electronic commutator circuit comprises solid state switching devices.
 9. The direct current brushless motor device of claim 1 wherein said electronic commutator circuit is configured to provide a three-phase stator coil switching sequence.
 10. The direct current brushless motor device of claim 1 wherein said printed circuit coil windings are coated with a ferrous material to increase the magnetic attraction between said coil windings and said rotor assembly permanent magnets at a rest position of the rotor assembly.
 11. The direct current brushless motor device of claim 1 wherein said printed circuit coil windings are coated with a ferrous material to increase the magnetic attraction between said coil windings and said rotor assembly permanent magnets at a rest position of the rotor assembly, said ferrous material coating comprising a nickel-gold plating.
 12. The direct current brushless motor device of claim 1 wherein said ring-shaped stator assembly further comprises a magnetic bridge said bridge comprising a band of ferrous material surrounding said printed circuit coil windings said magnetic bridge operative to connect and concentrate magnetic flux between said printed coil windings of said stator assembly and said rotor assembly permanent magnets.
 13. The direct current brushless motor device of claim 12 wherein said ring-shaped stator assembly further comprises a magnetic bridge, said bridge comprising a band of ferrous material surrounding said printed circuit coil windings, said band of ferrous material comprising a continuous wire wrapping of one or more layers of ferrous wire, said magnetic bridge operative to connect and concentrate magnetic flux between said printed coil windings of said stator assembly and said rotor assembly permanent magnets.
 14. The direct current brushless motor device of claim 12 wherein said magnetic bridge is a rotatable assembly mechanically connected to the rotor assembly.
 15. An integrated axial flow fan device comprising a direct current brushless motor assembly having a ring-shaped stator and a rotatable ring-shaped rotor disposed within said stator, said rotor comprising a central axis hub fan blade assembly whereby electromagnetic torque-energy developed by interacting magnetic fields of the rotor and stator causes rotation of the fan blade assembly around the rotor central axis.
 16. An integrated fluid impeller device comprising a direct current brushless motor assembly having a ring-shaped stator and a rotatable ring-shaped rotor disposed within said stator, said rotor comprising a central axis hub impeller blade assembly whereby electromagnetic torque-energy developed by interacting magnetic fields of the rotor and stator causes rotation of the impeller blade assembly around the rotor central axis.
 17. A motor stator coil assembly comprising a ring-shaped band of electrically insulating material having circumferentially placed printed circuit coil windings, said coil windings interconnected in a three-phase circuit and operative to generate a magnetic field in response to the flow of electrical current through said coil windings, said magnetic field operative to interact with a magnetic field of a rotor assembly of a motor, said interacting magnetic fields causing rotation of said rotor assembly.
 18. A motor stator coil assembly comprising a ring-shaped band substrate of electrically insulating material said substrate having circumferentially placed printed circuit coil windings, said coil windings arranged in layers on each side of said substrate, each layer comprising several pairs of coil windings, each pair of coil windings made as a spiral winding extending from the center of a start coil winding to the center of an end coil winding with the same turn direction of the spiral in relation to each coils center, said layers of coil windings are the same in a transparent view and are shifted linearly such that the center of a start coil winding on one layer is electrically connected to the center of an end coil winding on another layer using via's or copper plated holes, through the substrate.
 19. The motor stator coil assembly of claim 18 wherein said printed circuit coil windings are electrically connected to a commutator circuit.
 20. An integrated stator coil and housing assembly for a direct current brushless motor device comprising a ring shaped substrate formed as part of said housing assembly, said substrate having circumferentially placed printed circuit coil windings, said coil windings operative to generate a magnetic field in response to the flow of electrical current through said coil windings, said magnetic field operative to interact with a magnetic field of a rotor assembly of a motor, said interacting magnetic fields causing rotation of said rotor assembly.
 21. A method of manufacturing a motor stator coil assembly comprising: forming a ring-shaped band of electrically insulating material; placing printed circuit coil windings on at least one side of said band; and circumferentially arranging said printed circuit coil windings along said band to generate a magnetic field in response to the flow of electrical current through said coil windings, said magnetic field operative to interact with a magnetic field of a rotor assembly of a motor, said interacting magnetic fields causing rotation of said rotor assembly.
 22. A method of manufacturing a motor stator coil assembly comprising: forming a ring-shaped band substrate of electrically insulating material; and placing printed circuit coil windings along said substrate, said coil windings circumferentially arranged in layers on each side of said substrate, each layer comprising several pairs of coil windings, each pair of coil windings made as a spiral winding extending from the center of a start coil winding to the center of an end coil winding with the same turn direction of the spiral in relation to each coils center, said layers of coil windings are the same in a transparent view and are shifted linearly such that the center of a start coil winding on one layer is electrically connected to the center of an end coil winding on another layer using via's or copper plated holes through said substrate whereby said printed coil windings generate a magnetic field in response to the flow of electrical current through said coil windings, said magnetic field operative to interact with a magnetic field of a rotor assembly of a motor, said interacting magnetic fields causing rotation of said rotor assembly. 